Propagation Constant Difference Research Articles

Degradation of Polyester Composite Reinforced E-Glass Fiber with Calcium Carbonate Filler in Seawater

This research is concerned with composite materials that use CaCO3 as a reinforcing material in construction, especially subsea panels and buildings. Composite materials are solids composed of two or more materials that have their own properties and improve their properties when combined. In this experiment, glass fiber and CaCO3 were mixed in a certain composition and tested to evaluate the water absorption and mechanical strength of the composite. The results show that increasing temperature can increase water absorption, while the addition of CaCO3 has a significant effect on water absorption due to its hydrophilic properties. Water absorption in polyester composites is influenced by aging temperature and Calcium Carbonate powder filler, affecting tensile and bending strength. As aging temperature increases, mechanical strength decreases, composite having the highest tensile strength. Bending tests show debonding and splitting fault patterns due to glass fiber arrangement. With a deeper understanding of how CaCO3 affects composite materials under various conditions, this research can provide valuable insights for developing more durable composite materials suitable for construction applications, especially in corrosive environments such as subsea buildings.In this research, it proposes theoretically model to controlling on half-wave voltage of modulator, in which it uses studying the factor of effective of refractive index difference, this using analysis distribution of refractive index for LN material before and after voltage is applied (i.e., with and without applied voltage), and uses analysis a factor of propagation constant difference ??, before and after voltage is applied where it depends on the wavelength, these leads to it controls on the half-wave voltage V? using a reduction half-wave voltage up to 1V. Also, it achieves an excellent solution for solve the fundamental optical mode with effective factor is neff. Finally, the modulator with an effect effective refractive index difference have lower applied voltage up to 10V, and with an effective propagation constant difference the operating voltage is from value of 20V.

A Reduction of the Half-Wave Voltage for Lithium Niobate Electro-Optic Mach-Zehnder Modulator

In this research, it proposes theoretically model to controlling on half-wave voltage of modulator, in which it uses studying the factor of effective of refractive index difference, this using analysis distribution of refractive index for LN material before and after voltage is applied (i.e., with and without applied voltage), and uses analysis a factor of propagation constant difference ??, before and after voltage is applied where it depends on the wavelength, these leads to it controls on the half-wave voltage V? using a reduction half-wave voltage up to 1V. Also, it achieves an excellent solution for solve the fundamental optical mode with effective factor is neff. Finally, the modulator with an effect effective refractive index difference have lower applied voltage up to 10V, and with an effective propagation constant difference the operating voltage is from value of 20V.

Wideband compact phase shifter based on hybrid half-mode substrate integrated waveguide and spoof surface plasmon polariton

This paper proposes a wideband compact equal-length phase shifter based on the hybrid half-mode substrate integrated waveguide (HMSIW) and spoof surface plasmon polariton (SSPP) concept for the first time. The HMSIW transmission lines (TLs) with different widths result in different propagation constants. The difference of propagation constants between two HMSIW TLs with two different widths decreases as the frequency increases. Therefore, a wideband phase shifter cannot be designed by using this technique. In this paper, a series of half-butterfly grooves are etched on the top conductor layer of the HMSIW TL to compensate the phase shift. The combination of the SSPP and HMSIW structures provides a higher degree of freedom to keep the propagation constants difference constantly. Accordingly, a wideband response can be achieved by properly tuning the structure. Here, the dispersion characteristic of the butterfly-shaped HMSIW-SSPP can be adjusted by changing the width of the HMSIW and the radius and angle of the half-butterfly grooves. Moreover, the HMSIW-SSPP structure with half-butterfly grooves reduces both longitudinal and transverse dimensions of the proposed circuit. It has more slow-wave effects than the traditional counterpart with rectangular grooves. To validate the concept, a phase shifter is designed and fabricated on a single-layer substrate at the center frequency of 5.8 GHz covering WLAN. The simulated and measured results are in good agreement. The measured results show that the phase shifter has a fractional bandwidth of 31.7% with a phase error of , an insertion of dB, and a return loss of higher than 13.8 dB. Also, the size of the proposed phase shifter is .

Estimation of cover sensitivity of a planar polymer waveguide through double path broadband difference interferometeric analysis

Broadband difference interferometeric analysis of a double path planar polymer optical waveguide is presented for bio-sensing applications. Mathematical formulation of intensity of output signal is obtained using interferometeric analysis. Further, the dispersion equation is obtained by matching the field at core cladding interface that gives the cutoff film thickness for TE0 and TM0 modes in considered spectral range. The waveguide is analyzed by propagating either same polarized (TETE or TMTM) modes or unlike polarized (TETM) modes in the reference arm and sensing arm. It is observed that difference of propagation constant for same polarized mode increases with increase of wavelength while for unlike polarized modes it first increases up to a maximum value and then decreases in the considered wavelength range. The maxima of output interference signal shifted prominently with the cover refractive index for the wavelength range near the maximum value of propagation constant difference. The obtained sensitivity 9.226 for unlike polarized modes in arms is much larger than the sensitivity 0.071 of same polarized modes in arms.

Studies on Temperature and Strain Sensitivities of a Few-Mode Critical Wavelength Fiber Optic Sensor

This paper studied the relationship between the temperature/strain wavelength sensitivity of a fiber optic in-line Mach–Zehnder interferometer (MZI) sensor and the wavelength separation of the measured wavelength to the critical wavelength (CWL) in a CWL-existed interference spectrum formed by interference between LP01 and LP02 modes. The in-line MZI fiber optic sensor has been constructed by splicing a section of specially designed few-mode fiber (FMF), which supports LP01 and LP02 modes propagating in the fiber, between two pieces of single-mode fiber. The propagation constant difference, $\Delta \beta $ , between the LP01 and LP02 modes, changes non-monotonously with wavelength and reaches a maximum at the CWL. As a result, in the sensor operation, peaks on the different sides of the CWL then shift in opposite directions, and the associated temperature/strain sensitivities increase significantly when the measured wavelength points become close to the CWL, from both sides of the CWL. A theoretical analysis carried out has predicted that with this specified FMF sensor approach, the temperature/strain wavelength sensitivities are governed by the wavelength difference between the measured wavelength and the CWL. This conclusion was seen to agree well with the experimental results obtained. Combining the wavelength shifts of the peaks and the CWL in the transmission spectrum of the SFS structure, this paper has shown that this approach forms the basis of effective designs of high sensitivity sensors for multi-parameter detection and offering a large measurement range to satisfy the requirements needed for better industrial measurements.

Asymmetric Wavelength-Selective Directional Couplers as Fractional-Order Optical Differentiators

In this paper, the asymmetric wavelength-selective directional coupler (DC) is designed as a fractional-order optical differentiator. It is shown that the order of the optical differentiator is determined by the coupling coefficient and the propagation constant difference between the two waveguides in the coupler. The relation between the order of differentiator and the structure parameters of DC is analyzed. Optical differentiators with fractional orders of 0.47, 0.78, and 1.1 based on the asymmetric wavelength-selective DC are designed and analyzed, of which the processing errors are 10.04%, 6.11%, and 22.24%, and the energetic efficiencies are 20.61%, 19.62%, and 20.39%, respectively. The proposed design provides a competitive way for the fractional-order optical differentiator.

Characteristics of few-mode fibre and its application in simultaneous strain and temperature measurement

This paper discusses a novel detection scheme to measure strain and temperature simultaneously using a section of specially designed few mode fibre (FMF). The work shows that the propagation constant difference between LP01 and LP02 modes, Δβ, has a maximum at the critical wavelength (CWL) in the transmission spectrum. Theoretical analysis and experimental verification indicate that the peaks located on each side of the CWL shift to opposite directions under strain and temperature variations. The two peaks located closest to the CWL from both sides, Left Peak 1 and Right Peak 1, shift linearly with indeed different and high strain and temperature sensitivities, when an appropriate length of FMF is chosen, allowing such a device to be used to simultaneously measure strain and temperature over a known range.

Simultaneous Measurement of Strain and Temperature With a Few-Mode Fiber-Based Sensor

This paper proposes a novel detection scheme simultaneously to measure strain and temperature, based on a simple to construct device using a section of a specially designed few-mode fiber (FMF). The parameters and index profile of the FMF used as the key sensor element are such that the fiber supports only the LP01 and LP02 modes. The propagation constant difference between LP01 and LP02 modes Δ β has a maximum corresponding to the critical wavelength (CWL) in the fiber transmission spectrum. Because the two peaks located closest to the CWL from both sides, left peak 1 and right peak 1, shift in opposite directions, with different sensitivities under axial strain and temperature variations, the FMF device is capable of measuring the strain and temperature simultaneously. A theoretical analysis has been carried out as part of the design process and the experimental results obtained are found to agree well with the theoretical predictions. The characteristics of this sensor scheme are discussed in light of other competing approaches to simultaneous temperature and strain monitoring and are found to show advantages that suit several practical applications including compactness, ease of fabrication and implementation, relatively high sensitivities, and low cost.

Detection of Refractive Index Change From the Critical Wavelength of an Etched Few Mode Fiber

A novel scheme for the detection of refractive index change based on the mode interference in a special few mode fiber (FMF) is proposed in this paper. The parameters and index profile of the FMF used in the measurement are specifically designed so that only LP01 and LP02 modes are transmitted within the operation wavelength, and the propagation constant difference Δβ between these two modes reaches maximum at critical wavelength (CWL). An inline Mach–Zehnder interferometric sensor for the detection of surrounding refractive index (SRI) is constructed by splicing FMF with two sections of conventional single mode fiber. We demonstrated at the first time that the CWL will change monotonically with the change of SRI in the measurement range of 1.316–1.439. The experimental sensitivity of the CWL increases with the increase of SRI. A sensitiviy of 140.626 ± 12.560 nm/RIU in the range of 1.316–1.383 and a maximum sensitivity of 2489.796 ± 190.179 nm/RIU in the range of 1.433–1.439 were obtained, respectively, in the experiment. At present parameters of the etched FMF, the limit of detection of the refractive index is 3.413 × 10–4 RIU in the SRI range of 1.316–1.383, and 1.928 × 10–5 RIU in the SRI range of 1.433–1.439, respectively. The detection of SRI via monitoring the shift of CWL is superior to the traditional detection method via monitoring merely the shift of peak or dip wavelength of the transmission spectrum, since the latter usually suffers from limited measurement range and multivalue problem because it is difficult to identify and follow one specific peak or dip from the transmission spectrum especially if the system needs to reset in practical application. The novel detection scheme based on monitoring the shift of the exclusive CWL of FMF is promising in practical applications.

Double Dielectric Slab-Loaded Air-Filled SIW Phase Shifters for High-Performance Millimeter-Wave Integration

Phase shifters based on double dielectric slab-loaded air-filled substrate-integrated waveguide (SIW) are proposed for high-performance applications at millimeter-wave frequencies. The three-layered air-filled SIW, made of a low-cost multilayer printed circuit board process, allows for substantial loss reduction and power handling capability enhancement compared with the conventional dielectric-filled counterpart. It is of particular interest for millimeter-wave applications that generally require low-loss transmission and high-density power handling. Its top and bottom layers may make use of a low-cost standard substrate, such as FR-4, on which baseband analog or digital circuits can be implemented so to obtain very compact, low cost, and self-packaged millimeter-wave integrated systems compared with the systems based on rectangular waveguide while achieving higher performance than the systems based on the conventional SIW. In this paper, it is demonstrated that transmission loss can be further improved at millimeter-wave frequencies with an additional polishing of the top and bottom conductor surfaces. Over Ka-band, an improvement of average 1.56 dB/m is experimentally demonstrated. Using the air-filled SIW fabrication process, dielectric slabs can be implemented along conductive via rows without any additional process. Based on the propagation properties of the obtained double dielectric slab-loaded air-filled SIW, phase shifters are proposed. To obtain a broadband response, an equal-length compensated phase shifter made of two air-filled SIW structures, offering a reverse varying propagation constant difference against frequency, is proposed and demonstrated at Ka-band. Finally, a single dielectric slab phase shifter is investigated for comparison and its bandwidth limitation is highlighted.

Resonance optical activity in multihelicoidal optical fibers.

We have studied the effect of optical activity (OA) in optical fibers with multihelical distribution of refractive index profiles near the resonance wavelength, at which the conversion of an incident Gaussian beam into an optical vortex (and vice versa) takes place. We have shown that at such a wavelength the polarization vector of the input Gaussian beam rotates within the fiber at an average rate proportional to the difference in propagation constants of left- and right-circularly polarized optical vortices with the same topological charge. We also show that for certain fiber lengths the magnitude of OA can greatly exceed its average level and reach anomalously high values.

Polarization and propagation characteristics of switchable first-order azimuthally asymmetric beam generated in dual-mode fiber.

We report here the controlled generation of a linearly polarized first-order azimuthally asymmetric beam (F-AAB) in a dual-mode fiber (DMF) by appropriate superposition of selectively excited zeroth-order vector modes that are doughnut-shaped azimuthally symmetric beams (D-ASBs). We first demonstrate continually switching polarization mode structures having an identical two-lobe intensity profile (i.e., intra-F-AAB conversion). Then, under a distinct launching state, we generate mode structures progressively toggling between the doughnut-shaped profile and two-lobe pattern having dissimilar polarization orientations (i.e., F-AAB to D-ASB conversion). Interestingly, a decentralized elliptical Gaussian beam possessing homogenous spatial polarization is obtained by enhancing the contribution of the fundamental mode (HE₁₁/LP₀₁) in selectively excited F-AAB. A smoothly varying azimuth of the input beam in this situation resulted in redistribution of transverse energy procuring a unique and exciting unconventional two-grain T-polarized beam having mutually orthogonal state of polarization (SOP). All of the above three were achieved under a given set of launching conditions (tilt/offset) of a Gaussian mode (TEM₀₀) devised with changing SOP of the input beam. A strong modulation in the output beam characteristics was also observed with the variation in propagation distance (for a fixed input SOP) owing to the large difference in propagation constants of the participating modes (LP₀₁ and one of the F-AABs). Finally, this particular study led to a design for a low-cost highly sensitive strain measuring device based on tracking the centroid movement of the output intensity pattern. Each of our experimentally observed intensity/polarization distributions is theoretically mapped on a one-to-one basis considering a linear superposition of appropriately excited LP basis modes of the waveguide toward a complete understanding of the polarization and mode propagation in the dual-mode structure.

Distributed group birefringence measurement in a polarization-maintaining fiber using optical frequency-domain reflectometry

We propose to use optical frequency-domain reflectometry to measure distributed group birefringence along a section of polarization-maintaining fiber. Frequency dependence of the propagation constant difference along the fiber between the fast and slow modes can be determined. The scanning frequency bandwidth has influences on the measurement of the phase modal birefringence and beat length. Besides phase modal birefringence and beat length can be measured, distributed group birefringence along the fiber is obtained with a spatial resolution of 7.8cm.

Transmission Spectrum Characteristics for a Single-Mode-Multimode-Single-Mode Fiber Filter

We designed and demonstrated a single-mode-multimode-single-mode fiber filter using a step-indexed large-mode-area fiber, which has a critical wavelength at 1046 nm. A broad transmission peak or trough at 1046 nm is very sensitive to strain or temperature variation. The interference fringes on either side of the critical wavelength show blue or red shift, respectively, when the filter is subjected to strain and temperature changes. We simulated the transmission spectrum based on the interference of two modes, LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> and LP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> , and their propagation constant difference. The simulated spectrum matches reasonably well with the experimental spectrum. The filter can be used as a variable output coupler or for fiber optic sensors.

Ultra-low-loss CMOS-compatible waveguide crossing arrays based on multimode Bloch waves and imaginary coupling

We experimentally demonstrate broadband waveguide crossing arrays showing ultralow loss of 0.0 4dB/crossing (0.9%) on average and converging to 0.033 dB/crossing (0.075%) matching theory and cross-talk suppression over 35 dB in a CMOS-compatible geometry. The principle of operation is the tailored excitation of a low-loss spatial Bloch wave formed by matching the periodicity of the crossing array to the difference in propagation constants of the first- and third-order TE-like modes of a multimode silicon waveguide. Radiative scattering at the crossing points acts like a periodic imaginary-permittivity perturbation that couples two supermodes, which results in imaginary (radiative) propagation-constant splitting and gives rise to a low-loss, unidirectional breathing Bloch wave. This type of crossing array provides a robust implementation of a key component enabling dense photonic integration.

Comprehensive numerical analysis of mode coupling in few mode fibers for mode multiplexed transmission

Mode multiplexed transmission is a novel idea to increase the transmission capacity in a multiplicative order for optical fiber communication links. Mode coupling is one of the fundamental issues in this mode of transmission which limits the length of the span. In this paper we established the theoretical background of mode coupling in step index few mode fibers followed by a numerical analysis of a limited case of four spatial modes. We observed the relationship of coupling coefficients with physical parameters of optical fiber and impact of difference of propagation constants of coupling modes. In the end we suggested about reasonable selection of normalized frequency value of fiber by including the effects of group delay dispersion of coupling modes. Keyword Few Mode Fibers; Mode Coupling; Coupling Coefficients Abid munir, xiangjun xin, bo liu, Ashiq Hussain,Shahab ahmad Niazi, Abdul latif,Aftab hussain, Comprehensive numerical analysis of mode coupling in few mode fibers for mode multiplexed transmission, RNIS: Research Notes in Information Science, Volume 10, pp. 63 ~ 72, 2012

Analytical Expression of Average Power-Coupling Coefficients for Estimating Intercore Crosstalk in Multicore Fibers

In order to realize fast and accurate estimation of intercore crosstalk in bent multicore fibers (MCFs), an analytical expression of the average power-coupling coefficient (PCC) based on an exponential autocorrelation function is, for the first time, derived, resulting in no need for heavy numerical computations. It is revealed that, when the bending radius is large and the correlation length is large, the average PCC is inversely proportional to the correlation length and to the square of the propagation constant difference Δβ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mn</sub> between core m and core n, and when the bending radius is small and the correlation length is large, the average PCC is proportional to the bending radius and is independent of the correlation length. When the correlation length is small, on the other hand, the average PCC is proportional to the correlation length and is independent of the bending radius. For homogeneous MCFs (Δβ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mn</sub> = 0) with small bending radius, the average PCC coincides with the mean crosstalk increase per unit length derived from the coupled-mode theory of Hayashi et al. that is proportional to the bending radius. Average crosstalk values calculated by using the analytical expression derived here are in excellent agreement with those of numerical solutions of coupled-power equations, irrespective of the values of bending radius and correlation length.

Optical sensing of nanoparticles in the infrared by use of silica nanowires

We numerically investigate an optical sensor in the infrared based on a Mach–Zehnder interferometer (MZI) assembled with two single-mode silica nanowires immersed in acetonitrile. We propose to use acetonitrile as the detecting solution because, in contrast to water which has very high losses in the infrared, it has negligible losses at important wavelengths of 1,300 and 1550 nm. By solving for the fundamental mode of a three-layer nanowire, we calculate the propagation constant difference between the sensing and reference arms at the output of the MZI optical sensor. For nanoparticles with a size of 12 nm and an index of refraction of 1.4, the sensitivity of the optical sensor becomes a maximum for a wire diameter of 1.23 μm. An optical sensor operating at a wavelength of 325 nm and using water as the detecting solution requires nanowires with a diameter of 240 nm, which is much more difficult to implement.

Strain Effect on Differential Phase Sensitivity in Two-Mode Fibers

The modular differential phase characteristics of elliptical core fiber (ECF) and high- birefringence photonic crystal fiber (HB-PCF) are presented. The results show that HB-PCF has a larger range of wavelengths for two-mode operating than ECF. And when the longitudinal strain is applied on the fiber, the modular propagation constant difference between and modes is the most important factor for differential phase sensitivity. With the wavelength increases, the differential phase sensitivity of ECF decreases whereas that of HB-PCF changes in opposite way. And HB-PCF is more sensitive to strain than ECF.

Nonreciprocal optical Bloch oscillations in garnet/silicon-on-insulator waveguide arrays

ABSTRACTWe show that nonreciprocal Bloch-like oscillations can emerge in passive optical waveguide arrays with linearly growing effective index in the absence of loss or gain. Spectral asymmetry, a difference in propagation constants and Bloch oscillation periods in opposite propagation directions, are established by imposing different vertical spatial index gradients at the substrate/core, and core/cover interfaces in the presence of transverse magnetization. A model system consisting of an array of transversely magnetized asymmetric garnet/silicon-on-insulator waveguides is presented.